IgD is the immunoglobulin class that is present on the surface of the majority of B cells, but virtually absent from or very low in serum. Many theories about the role of IgD in triggering of B cells by antigen, in induction of proliferation and differentiation of the cells have been put forth, but none have been sufficiently substantiated. In recent years considerable progress has been made concerning elucidation of the structure of Ig D and the localization of the gene for Delta chain production within the CH gene complex. Ig D is, therefore, a subject which can assemble a varied company of scientists for productive and stimulating discussions. No previous meeting on IgD has been organized and the only series of minireviews published on Ig D dates from 1977. The fact that scientists from various disciplines will discuss the relevance of IgD to B cell function, and that their findings will be published in a volume of the Annals of the New York Academy of Sciences, should serve to bring the scientific community up-to-date with the current status of information on IgD as well as stimulate interest in the subject.